DHCPD and option-82 problem

Denis Laventure Denis_Laventure at uqac.ca
Wed May 28 14:55:10 UTC 2014


That's what I did with that line like I said:

>> > if exists agent.circuit-id {
>> >   log (info, concat("DEBUG: (option-82 raw) ", client-mac-address, "
>> > - ", binary-to-ascii (16, 8, ":", option agent.circuit-id))); }

It doesn't enter the "if exists" condition when the packet is received by the daemon... Even if I remove the condition and let the log statement in, I don't get anything.

I didn't find any pattern yet, I get this problem with various devices even home routers like a D-Link...

When I capture packet from all those devices, I always get option-82 in tcpdump/wireshark and the string is exactly as I entered it in the class definition/host-identifier statement. But the daemon doesn't seems to catch it. Very strange...

Denis

-----Message d'origine-----
De : dhcp-users-bounces at lists.isc.org [mailto:dhcp-users-bounces at lists.isc.org] De la part de Glenn Satchell
Envoyé : 22 mai 2014 19:10
À : Users of ISC DHCP
Objet : RE: DHCPD and option-82 problem

What seems to be happenning is that the packet is not matching the class RES-4D, otherwise it would print the DEBUG line to the log. Only way this could be is if the option agent.circuit-id does not match. And if it doesn't match the class it is denied in that pool, and gets 'no free leases' message because it doesn't match any pool.

Perhaps adding another log line on the body of the dhcpd.conf to record what the option agent.circuit-id is for those failing systems and see what happens. Something like this, so you can grep for DEBUG2 maybe:

log(info,concat("DEBUG2: RESD-4D ",client-mac-address," circuit-id ",option agent.circuit-id));

With dhcp snooping on the switch, the switch has to re-write the packet to insert the circuit-id, so perhaps the resulting packet then becomes invalid for dhcpd in some other way?

Need to very carefully look at the packet trace and see if any other fields have different or odd looking values. It may be the circuit-id is ok, but something else is not.

Can you create a list of hostnames, mac addresses, client os, etc, that do and don't work and look for a pattern there?

regards,
-glenn

On Thu, May 22, 2014 11:33 pm, Denis Laventure wrote:
> That's what I think too. It works with the IOS dhcp service with
> option-82 on the cisco router so the DISCOVER packet seems right, even
> tcpdump decodes it on the server end... But I don't know any other
> method to debug the dhcp server other than the log statement. And I'm
> not able to debug the code (my programming skills are not as good as
> they were 20 years ago!).
>
> Denis Laventure
>
> -----Message d'origine-----
> De : dhcp-users-bounces at lists.isc.org
> [mailto:dhcp-users-bounces at lists.isc.org] De la part de Chuck Anderson
> Envoyé : 22 mai 2014 08:58 À : dhcp-users at lists.isc.org Objet : Re:
> DHCPD and option-82 problem
>
> If your capture was from the DHCP server end, and it shows the
> Option-82 in the capture for the packet coming in from the client
> through the relay, but the server doesn't log anything about the
> match, then I don't think the problem could be with the switch or router or relay-agent.
>  It sounds like a code problem (bug) with dhcpd.
>
> On Thu, May 22, 2014 at 07:53:12AM -0400, Denis Laventure wrote:
>> Good catch Glenn! :)
>>
>> Yeah this was my fault, I had log from RESD-4D but capture from
>> RESD-4B... I changed the MAC on the capture log to post it here so no
>> one would see it, but I forgot to change the option-82 string. I
>> should have double-checked before posting :)
>>
>> Anyway the problem is the same with the right string.
>>
>> I will continue to investigate with the "ip dhcp snooping trust" like
>> Joseph suggested, perhaps this is a case for a TAC call... I have the
>> problem with 2 type of cisco switches with different IOS version
>> (12.x vs 15.x)...
>>
>> Thanks,
>> Denis
>>
>> -----Message d'origine-----
>> De : dhcp-users-bounces at lists.isc.org
>> [mailto:dhcp-users-bounces at lists.isc.org] De la part de Glenn
>> Satchell Envoyé : 22 mai 2014 04:11 À : Users of ISC DHCP Objet : RE:
>> DHCPD and
>> option-82 problem
>>
>> The circuit-id is different between the dhcpd.conf and the packet
>> capture.
>> Last number is 44 in dhcpd.conf and 42 in tcpdump output. Is that
>> just a copy/paste error or might be significant?
>>
>> class "RESD-4D" {
>>    match if option agent.circuit-id=1:7:52:45:53:44:2d:34:44;
>>
>> Agent Circuit ID: 0107524553442d3442
>>
>> regards,
>> -glenn
>>
>> On Thu, May 22, 2014 3:19 am, Denis Laventure wrote:
>> > Just to clarify, I have done this for several years now. I used
>> > Method
>> > 1 and/or Method 2 without problem. I just found out by some clients
>> > that sometimes it doesn't work with there device (about 20 clients
>> > / PC, Mac, Router, etc).
>> >
>> > When the packet get to the dhcp server, it contains option-82
>> > (checked by
>> > tcpdump) but I get no log from my dhcp daemon using this log
>> > statement in dhcpd.conf :
>> >
>> > if exists agent.circuit-id {
>> >   log (info, concat("DEBUG: (option-82 raw) ", client-mac-address, "
>> > - ", binary-to-ascii (16, 8, ":", option agent.circuit-id))); }
>> >
>> > When option-82 get used and the client get an IP, I see the log
>> > from this statement, but when I get the no free leases error,
>> > there's no
>> > option-82 log... The daemon doesn't seems to recognize option-82...
>> > But tcpdump/wireshark decodes the option-82 from the same
>> > DHCPDISCOVER without problem.
>> >
>> > Thanks,
>> > Denis Laventure
>> >
>> > De : dhcp-users-bounces at lists.isc.org
>> > [mailto:dhcp-users-bounces at lists.isc.org] De la part de Denis
>> > Laventure Envoyé : 21 mai 2014 12:08 À : dhcp-users at lists.isc.org
>> > Objet : DHCPD and option-82 problem
>> >
>> > Hi,
>> >
>> > We have about 300 connections on our university dormitory and we
>> > use
>> > option-82 to assign one fixed IP to every chamber.
>> > Everything works fine but I sometimes find that some clients don't
>> > get an IP and keep sending DHCPDISCOVER continually. Sometimes it's
>> > a Windows 7 client, sometimes it's a D-LINK Router or a Mac.
>> >
>> > I captured the requests from one client and everything seems
>> > normal, it even have option-82 inserted by the relay.
>> > In my dhcpd log, the dhcpd daemon doesn't decode it option-82 and
>> > the option agent.circuit-id is empty. (tcpdump/wireshark capture
>> > below) I get the usual "no free leases" since option-82 isn't
>> recognized.
>> > (dhcpd log below)
>> >
>> > Is there a way to debug received DHCPDICOVER packets (other than
>> > log or
>> > tcpdump) that I could check to make sure option-82 is present and
>> > decoded by the daemon?
>> > Why dhcp daemon doesn't decode option-82 if it's in the packet?
>> >
>> > I'm on Linux RHEL 5.10 and using ISC DHCPD version 4.3.0 (in
>> > failover). I tried downgrading to version 4.2.0 and I have the same
>> problem.
>> >
>> > For now, I'm using a Cisco 3560 as dhcp server with option-82 and
>> > all the clients (even the ones that don't work with isc dhcpd)
>> > works. I don't want to keep using the Cisco router for dhcp, I want
>> > to return to my isc dhcp server but I can't because of that problem...
>> >
>> > Thanks,
>> > Denis Laventure
>> >
>> > ===================================================================
>> > = == ==========================================
>> >
>> > Aditional informations:
>> >
>> > Client Switch: cisco WS-C2960S-F48TS-L
>> >
>> > sh ver
>> > Cisco IOS Software, C2960S Software (C2960S-UNIVERSALK9-M), Version
>> > 15.2(1)E2, RELEASE SOFTWARE (fc1)
>> >
>> > interface FastEthernet2/0/17
>> > ip dhcp snooping vlan 261 information option format-type circuit-id
>> > string RESD-4D
>> >
>> >
>> > ===================================================================
>> > = == ==========================================
>> >
>> > Method 1 (Class and Pool):
>> >
>> > subnet 172.17.11.0 netmask 255.255.255.0 {
>> >                                ...
>> >         pool { range 172.17.11.80; allow members of "RESD-4D"; }
>> >                                ...
>> > }
>> >
>> > set client-mac-address = concat (
>> >   suffix (concat ("0", binary-to-ascii (16, 8, "",
>> > substring(hardware,1,1))),2), ":",
>> >   suffix (concat ("0", binary-to-ascii (16, 8, "",
>> > substring(hardware,2,1))),2), ":",
>> >   suffix (concat ("0", binary-to-ascii (16, 8, "",
>> > substring(hardware,3,1))),2), ":",
>> >   suffix (concat ("0", binary-to-ascii (16, 8, "",
>> > substring(hardware,4,1))),2), ":",
>> >   suffix (concat ("0", binary-to-ascii (16, 8, "",
>> > substring(hardware,5,1))),2), ":",
>> >   suffix (concat ("0", binary-to-ascii (16, 8, "",
>> > substring(hardware,6,1))),2)
>> > );
>> >
>> > class "RESD-4D" {match if option
>> > agent.circuit-id=1:7:52:45:53:44:2d:34:44; log(info,concat("DEBUG:
>> > RESD-4D ",client-mac-address));}
>> >
>> > Result:
>> > ...
>> > May  6 16:41:23 dhcpa dhcpd: DHCPDISCOVER from 74:d0:2b:e9:82:0d
>> > via
>> > 172.17.11.1: network 172.17.11.0/24: no free leases May  6 16:41:54
>> > dhcpa dhcpd: DHCPDISCOVER from 74:d0:2b:e9:82:0d via
>> > 172.17.11.1: network 172.17.11.0/24: no free leases May  6 16:41:59
>> > dhcpa dhcpd: DHCPDISCOVER from 74:d0:2b:e9:82:0d via
>> > 172.17.11.1: network 172.17.11.0/24: no free leases ...
>> >
>> > Working client get:
>> > May  6 08:14:07 dhcpa dhcpd: DEBUG: (client info) 172.17.11.79 -
>> > 74:86:7a:2b:90:16 - MSFT 5.0 - 1,f,3,6,2c,2e,2f,1f,21,79,f9,fc,2b
>> > May  6 08:14:07 dhcpa dhcpd: DEBUG: (option-82 raw)
>> > 74:86:7a:2b:90:16
>> > -
>> > 1:7:52:45:53:44:2d:34:43
>> > May  6 08:14:07 dhcpa dhcpd: DEBUG: RESD-4C 74:86:7a:2b:90:16 May
>> > 6
>> > 08:14:07 dhcpa dhcpd: DHCPDISCOVER from 74:86:7a:2b:90:16 via
>> > 172.17.11.1
>> > May  6 08:14:07 dhcpa dhcpd: DHCPOFFER on 172.17.11.79 to
>> > 74:86:7a:2b:90:16 (Inspiron3521) via 172.17.11.1 May  6 08:14:07
>> > dhcpa
>> > dhcpd: DEBUG: (client info) 172.17.11.79 -
>> > 74:86:7a:2b:90:16 - MSFT 5.0 - 1,f,3,6,2c,2e,2f,1f,21,79,f9,fc,2b
>> > May  6 08:14:07 dhcpa dhcpd: DEBUG: (option-82 raw)
>> > 74:86:7a:2b:90:16
>> > -
>> > 1:7:52:45:53:44:2d:34:43
>> > May  6 08:14:07 dhcpa dhcpd: DEBUG: (option-82 cid)
>> > IP:172.17.11.79, MAC:74:86:7a:2b:90:16,
>> > CID:1:7:52:45:53:44:2d:34:43 May  6 08:14:07 dhcpa dhcpd: DEBUG:
>> > RESD-4C 74:86:7a:2b:90:16 May  6 08:14:07 dhcpa
>> > dhcpd: DHCPREQUEST for 172.17.11.79 (192.168.1.10) from
>> > 74:86:7a:2b:90:16 (Inspiron3521) via 172.17.11.1 May  6 08:14:07
>> > dhcpa
>> > dhcpd: DHCPACK on 172.17.11.79 to 74:86:7a:2b:90:16
>> > (Inspiron3521) via 172.17.11.1
>> >
>> > ===================================================================
>> > = == ==========================================
>> >
>> > Method 2 (host-identifier):
>> >
>> > host RESD-4D    { host-identifier option agent.circuit-id
>> > 1:7:52:45:53:44:2d:34:44; fixed-address 172.17.11.80; }
>> >
>> > Result:
>> > ...
>> > May  6 17:02:37 dhcpa dhcpd: DHCPDISCOVER from 74:d0:2b:e9:82:0d
>> > via
>> > 172.17.11.1: network 172.17.11.0/24: no free leases May  6 17:02:54
>> > dhcpa dhcpd: DHCPDISCOVER from 74:d0:2b:e9:82:0d via
>> > 172.17.11.1: network 172.17.11.0/24: no free leases May  6 17:03:26
>> > dhcpa dhcpd: DHCPDISCOVER from 74:d0:2b:e9:82:0d via
>> > 172.17.11.1: network 172.17.11.0/24: no free leases ...
>> >
>> > ===================================================================
>> > = == ==========================================
>> >
>> > TCPDUMP/WIRESHARK LOG (5 DHCPDISCOVER)
>> >
>> > No.     Time        Source                Destination
>> Protocol
>> > Length Info
>> >       1 0.000000    172.17.11.1           192.168.1.10         DHCP
>> > 352    DHCP Discover - Transaction ID 0xcab50e69
>> >
>> > Frame 1: 352 bytes on wire (2816 bits), 352 bytes captured (2816
>> > bits) Ethernet II, Src: 10:8c:cf:28:5a:40 (10:8c:cf:28:5a:40), Dst:
>> > 00:1e:c9:d7:2c:d8 (00:1e:c9:d7:2c:d8) Internet Protocol Version 4,
>> > Src: 172.17.11.1 (172.17.11.1), Dst:
>> > 192.168.1.10 (192.168.1.10)
>> > User Datagram Protocol, Src Port: 67 (67), Dst Port: 67 (67)
>> > Bootstrap Protocol
>> >     Message type: Boot Request (1)
>> >     Hardware type: Ethernet (0x01)
>> >     Hardware address length: 6
>> >     Hops: 1
>> >     Transaction ID: 0xcab50e69
>> >     Seconds elapsed: 0
>> >     Bootp flags: 0x8000 (Broadcast)
>> >     Client IP address: 0.0.0.0 (0.0.0.0)
>> >     Your (client) IP address: 0.0.0.0 (0.0.0.0)
>> >     Next server IP address: 0.0.0.0 (0.0.0.0)
>> >     Relay agent IP address: 172.17.11.1 (172.17.11.1)
>> >     Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
>> >     Client hardware address padding: 00000000000000000000
>> >     Server host name not given
>> >     Boot file name not given
>> >     Magic cookie: DHCP
>> >     Option: (53) DHCP Message Type
>> >         Length: 1
>> >         DHCP: Discover (1)
>> >     Option: (61) Client identifier
>> >         Length: 7
>> >         Hardware type: Ethernet (0x01)
>> >         Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
>> >     Option: (12) Host Name
>> >         Length: 7
>> >         Host Name: SAMSUNG
>> >     Option: (60) Vendor class identifier
>> >         Length: 8
>> >         Vendor class identifier: MSFT 5.0
>> >     Option: (55) Parameter Request List
>> >         Length: 13
>> >         Parameter Request List Item: (1) Subnet Mask
>> >         Parameter Request List Item: (15) Domain Name
>> >         Parameter Request List Item: (3) Router
>> >         Parameter Request List Item: (6) Domain Name Server
>> >         Parameter Request List Item: (44) NetBIOS over TCP/IP Name
>> Server
>> >         Parameter Request List Item: (46) NetBIOS over TCP/IP Node
>> Type
>> >         Parameter Request List Item: (47) NetBIOS over TCP/IP Scope
>> >         Parameter Request List Item: (31) Perform Router Discover
>> >         Parameter Request List Item: (33) Static Route
>> >         Parameter Request List Item: (121) Classless Static Route
>> >        Parameter Request List Item: (249) Private/Classless Static
>> > Route
>> > (Microsoft)
>> >         Parameter Request List Item: (252) Private/Proxy autodiscovery
>> >         Parameter Request List Item: (43) Vendor-Specific Information
>> >     Option: (82) Agent Information Option
>> >         Length: 21
>> >         Option 82 Suboption: (1) Agent Circuit ID
>> >             Length: 9
>> >             Agent Circuit ID: 0107524553442d3442
>> >         Option 82 Suboption: (2) Agent Remote ID
>> >             Length: 8
>> >             Agent Remote ID: 0006f84f5742d700
>> >     Option: (255) End
>> >         Option End: 255
>> >
>> > No.     Time        Source                Destination
>> Protocol
>> > Length Info
>> >       2 4.944200    172.17.11.1           192.168.1.10         DHCP
>> > 352    DHCP Discover - Transaction ID 0xcab50e69
>> >
>> > Frame 2: 352 bytes on wire (2816 bits), 352 bytes captured (2816
>> > bits) Ethernet II, Src: 10:8c:cf:28:5a:40 (10:8c:cf:28:5a:40), Dst:
>> > 00:1e:c9:d7:2c:d8 (00:1e:c9:d7:2c:d8) Internet Protocol Version 4,
>> > Src: 172.17.11.1 (172.17.11.1), Dst:
>> > 192.168.1.10 (192.168.1.10)
>> > User Datagram Protocol, Src Port: 67 (67), Dst Port: 67 (67)
>> > Bootstrap Protocol
>> >     Message type: Boot Request (1)
>> >     Hardware type: Ethernet (0x01)
>> >     Hardware address length: 6
>> >     Hops: 1
>> >     Transaction ID: 0xcab50e69
>> >     Seconds elapsed: 4
>> >     Bootp flags: 0x8000 (Broadcast)
>> >     Client IP address: 0.0.0.0 (0.0.0.0)
>> >     Your (client) IP address: 0.0.0.0 (0.0.0.0)
>> >     Next server IP address: 0.0.0.0 (0.0.0.0)
>> >     Relay agent IP address: 172.17.11.1 (172.17.11.1)
>> >     Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
>> >     Client hardware address padding: 00000000000000000000
>> >     Server host name not given
>> >     Boot file name not given
>> >     Magic cookie: DHCP
>> >     Option: (53) DHCP Message Type
>> >         Length: 1
>> >         DHCP: Discover (1)
>> >     Option: (61) Client identifier
>> >         Length: 7
>> >         Hardware type: Ethernet (0x01)
>> >         Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
>> >     Option: (12) Host Name
>> >         Length: 7
>> >         Host Name: SAMSUNG
>> >     Option: (60) Vendor class identifier
>> >         Length: 8
>> >         Vendor class identifier: MSFT 5.0
>> >     Option: (55) Parameter Request List
>> >         Length: 13
>> >         Parameter Request List Item: (1) Subnet Mask
>> >         Parameter Request List Item: (15) Domain Name
>> >         Parameter Request List Item: (3) Router
>> >         Parameter Request List Item: (6) Domain Name Server
>> >         Parameter Request List Item: (44) NetBIOS over TCP/IP Name
>> Server
>> >         Parameter Request List Item: (46) NetBIOS over TCP/IP Node
>> Type
>> >         Parameter Request List Item: (47) NetBIOS over TCP/IP Scope
>> >         Parameter Request List Item: (31) Perform Router Discover
>> >         Parameter Request List Item: (33) Static Route
>> >         Parameter Request List Item: (121) Classless Static Route
>> >         Parameter Request List Item: (249) Private/Classless Static
>> > Route
>> > (Microsoft)
>> >         Parameter Request List Item: (252) Private/Proxy autodiscovery
>> >         Parameter Request List Item: (43) Vendor-Specific Information
>> >     Option: (82) Agent Information Option
>> >         Length: 21
>> >         Option 82 Suboption: (1) Agent Circuit ID
>> >             Length: 9
>> >             Agent Circuit ID: 0107524553442d3442
>> >         Option 82 Suboption: (2) Agent Remote ID
>> >             Length: 8
>> >             Agent Remote ID: 0006f84f5742d700
>> >     Option: (255) End
>> >         Option End: 255
>> >
>> > No.     Time        Source                Destination
>> Protocol
>> > Length Info
>> >       3 17.047575   172.17.11.1           192.168.1.10         DHCP
>> > 352    DHCP Discover - Transaction ID 0xa2024d9e
>> >
>> > Frame 3: 352 bytes on wire (2816 bits), 352 bytes captured (2816
>> > bits) Ethernet II, Src: 10:8c:cf:28:5a:40 (10:8c:cf:28:5a:40), Dst:
>> > 00:1e:c9:d7:2c:d8 (00:1e:c9:d7:2c:d8) Internet Protocol Version 4,
>> > Src: 172.17.11.1 (172.17.11.1), Dst:
>> > 192.168.1.10 (192.168.1.10)
>> > User Datagram Protocol, Src Port: 67 (67), Dst Port: 67 (67)
>> > Bootstrap Protocol
>> >     Message type: Boot Request (1)
>> >     Hardware type: Ethernet (0x01)
>> >     Hardware address length: 6
>> >     Hops: 1
>> >     Transaction ID: 0xa2024d9e
>> >     Seconds elapsed: 0
>> >     Bootp flags: 0x0000 (Unicast)
>> >     Client IP address: 0.0.0.0 (0.0.0.0)
>> >     Your (client) IP address: 0.0.0.0 (0.0.0.0)
>> >     Next server IP address: 0.0.0.0 (0.0.0.0)
>> >     Relay agent IP address: 172.17.11.1 (172.17.11.1)
>> >     Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
>> >     Client hardware address padding: 00000000000000000000
>> >     Server host name not given
>> >     Boot file name not given
>> >     Magic cookie: DHCP
>> >    Option: (53) DHCP Message Type
>> >         Length: 1
>> >         DHCP: Discover (1)
>> >     Option: (61) Client identifier
>> >         Length: 7
>> >         Hardware type: Ethernet (0x01)
>> >         Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
>> >     Option: (12) Host Name
>> >         Length: 7
>> >         Host Name: SAMSUNG
>> >     Option: (60) Vendor class identifier
>> >         Length: 8
>> >         Vendor class identifier: MSFT 5.0
>> >     Option: (55) Parameter Request List
>> >         Length: 13
>> >         Parameter Request List Item: (1) Subnet Mask
>> >         Parameter Request List Item: (15) Domain Name
>> >         Parameter Request List Item: (3) Router
>> >         Parameter Request List Item: (6) Domain Name Server
>> >         Parameter Request List Item: (44) NetBIOS over TCP/IP Name
>> Server
>> >         Parameter Request List Item: (46) NetBIOS over TCP/IP Node
>> Type
>> >         Parameter Request List Item: (47) NetBIOS over TCP/IP Scope
>> >         Parameter Request List Item: (31) Perform Router Discover
>> >         Parameter Request List Item: (33) Static Route
>> >         Parameter Request List Item: (121) Classless Static Route
>> >         Parameter Request List Item: (249) Private/Classless Static
>> > Route
>> > (Microsoft)
>> >         Parameter Request List Item: (252) Private/Proxy autodiscovery
>> >         Parameter Request List Item: (43) Vendor-Specific Information
>> >     Option: (82) Agent Information Option
>> >         Length: 21
>> >         Option 82 Suboption: (1) Agent Circuit ID
>> >             Length: 9
>> >             Agent Circuit ID: 0107524553442d3442
>> >         Option 82 Suboption: (2) Agent Remote ID
>> >             Length: 8
>> >             Agent Remote ID: 0006f84f5742d700
>> >     Option: (255) End
>> >         Option End: 255
>> >
>> > No.     Time        Source                Destination
>> Protocol
>> > Length Info
>> >       4 20.667474   172.17.11.1           192.168.1.10         DHCP
>> > 352    DHCP Discover - Transaction ID 0xa2024d9e
>> >
>> > Frame 4: 352 bytes on wire (2816 bits), 352 bytes captured (2816
>> > bits) Ethernet II, Src: 10:8c:cf:28:5a:40 (10:8c:cf:28:5a:40), Dst:
>> > 00:1e:c9:d7:2c:d8 (00:1e:c9:d7:2c:d8) Internet Protocol Version 4,
>> > Src: 172.17.11.1 (172.17.11.1), Dst:
>> > 192.168.1.10 (192.168.1.10)
>> > User Datagram Protocol, Src Port: 67 (67), Dst Port: 67 (67)
>> > Bootstrap Protocol
>> >     Message type: Boot Request (1)
>> >     Hardware type: Ethernet (0x01)
>> >     Hardware address length: 6
>> >     Hops: 1
>> >     Transaction ID: 0xa2024d9e
>> >     Seconds elapsed: 3
>> >     Bootp flags: 0x0000 (Unicast)
>> >     Client IP address: 0.0.0.0 (0.0.0.0)
>> >     Your (client) IP address: 0.0.0.0 (0.0.0.0)
>> >     Next server IP address: 0.0.0.0 (0.0.0.0)
>> >     Relay agent IP address: 172.17.11.1 (172.17.11.1)
>> >     Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
>> >     Client hardware address padding: 00000000000000000000
>> >     Server host name not given
>> >     Boot file name not given
>> >     Magic cookie: DHCP
>> >     Option: (53) DHCP Message Type
>> >         Length: 1
>> >         DHCP: Discover (1)
>> >     Option: (61) Client identifier
>> >         Length: 7
>> >         Hardware type: Ethernet (0x01)
>> >         Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
>> >     Option: (12) Host Name
>> >         Length: 7
>> >         Host Name: SAMSUNG
>> >     Option: (60) Vendor class identifier
>> >         Length: 8
>> >         Vendor class identifier: MSFT 5.0
>> >     Option: (55) Parameter Request List
>> >         Length: 13
>> >         Parameter Request List Item: (1) Subnet Mask
>> >         Parameter Request List Item: (15) Domain Name
>> >         Parameter Request List Item: (3) Router
>> >         Parameter Request List Item: (6) Domain Name Server
>> >         Parameter Request List Item: (44) NetBIOS over TCP/IP Name
>> Server
>> >         Parameter Request List Item: (46) NetBIOS over TCP/IP Node
>> Type
>> >         Parameter Request List Item: (47) NetBIOS over TCP/IP Scope
>> >         Parameter Request List Item: (31) Perform Router Discover
>> >         Parameter Request List Item: (33) Static Route
>> >         Parameter Request List Item: (121) Classless Static Route
>> >         Parameter Request List Item: (249) Private/Classless Static
>> > Route
>> > (Microsoft)
>> >         Parameter Request List Item: (252) Private/Proxy autodiscovery
>> >         Parameter Request List Item: (43) Vendor-Specific Information
>> >     Option: (82) Agent Information Option
>> >         Length: 21
>> >         Option 82 Suboption: (1) Agent Circuit ID
>> >             Length: 9
>> >             Agent Circuit ID: 0107524553442d3442
>> >         Option 82 Suboption: (2) Agent Remote ID
>> >             Length: 8
>> >             Agent Remote ID: 0006f84f5742d700
>> >     Option: (255) End
>> >         Option End: 255
>> >
>> > No.     Time        Source                Destination
>> Protocol
>> > Length Info
>> >       5 28.074747   172.17.11.1           192.168.1.10         DHCP
>> > 352    DHCP Discover - Transaction ID 0xa2024d9e
>> >
>> > Frame 5: 352 bytes on wire (2816 bits), 352 bytes captured (2816
>> > bits) Ethernet II, Src: 10:8c:cf:28:5a:40 (10:8c:cf:28:5a:40), Dst:
>> > 00:1e:c9:d7:2c:d8 (00:1e:c9:d7:2c:d8) Internet Protocol Version 4,
>> > Src: 172.17.11.1 (172.17.11.1), Dst:
>> > 192.168.1.10 (192.168.1.10)
>> > User Datagram Protocol, Src Port: 67 (67), Dst Port: 67 (67)
>> > Bootstrap Protocol
>> >     Message type: Boot Request (1)
>> >     Hardware type: Ethernet (0x01)
>> >     Hardware address length: 6
>> >     Hops: 1
>> >     Transaction ID: 0xa2024d9e
>> >     Seconds elapsed: 11
>> >     Bootp flags: 0x0000 (Unicast)
>> >     Client IP address: 0.0.0.0 (0.0.0.0)
>> >     Your (client) IP address: 0.0.0.0 (0.0.0.0)
>> >     Next server IP address: 0.0.0.0 (0.0.0.0)
>> >     Relay agent IP address: 172.17.11.1 (172.17.11.1)
>> >     Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
>> >     Client hardware address padding: 00000000000000000000
>> >     Server host name not given
>> >     Boot file name not given
>> >     Magic cookie: DHCP
>> >     Option: (53) DHCP Message Type
>> >         Length: 1
>> >         DHCP: Discover (1)
>> >     Option: (61) Client identifier
>> >         Length: 7
>> >         Hardware type: Ethernet (0x01)
>> >         Client MAC address: 74:d0:2b:e9:82:0d (74:d0:2b:e9:82:0d)
>> >     Option: (12) Host Name
>> >         Length: 7
>> >         Host Name: SAMSUNG
>> >     Option: (60) Vendor class identifier
>> >         Length: 8
>> >         Vendor class identifier: MSFT 5.0
>> >     Option: (55) Parameter Request List
>> >         Length: 13
>> >         Parameter Request List Item: (1) Subnet Mask
>> >         Parameter Request List Item: (15) Domain Name
>> >         Parameter Request List Item: (3) Router
>> >         Parameter Request List Item: (6) Domain Name Server
>> >         Parameter Request List Item: (44) NetBIOS over TCP/IP Name
>> Server
>> >         Parameter Request List Item: (46) NetBIOS over TCP/IP Node
>> Type
>> >         Parameter Request List Item: (47) NetBIOS over TCP/IP Scope
>> >         Parameter Request List Item: (31) Perform Router Discover
>> >         Parameter Request List Item: (33) Static Route
>> >         Parameter Request List Item: (121) Classless Static Route
>> >         Parameter Request List Item: (249) Private/Classless Static
>> > Route
>> > (Microsoft)
>> >         Parameter Request List Item: (252) Private/Proxy autodiscovery
>> >         Parameter Request List Item: (43) Vendor-Specific Information
>> >     Option: (82) Agent Information Option
>> >         Length: 21
>> >         Option 82 Suboption: (1) Agent Circuit ID
>> >             Length: 9
>> >             Agent Circuit ID: 0107524553442d3442
>> >         Option 82 Suboption: (2) Agent Remote ID
>> >             Length: 8
>> >             Agent Remote ID: 0006f84f5742d700
>> >     Option: (255) End
>> >         Option End: 255
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